The present invention pertains to a mixture of a halogenated phenoxy resin and an advanced epoxy resin, laminating varnishes containing same and laminates prepared therefrom.
Electrical laminates are prepared by blending minor amounts of a phenoxy resin with an advanced epoxy resin, curing agent therefor and solvents if required. Shell Chemical Company in Bulletin SC:850-85 discloses the use of ultrahigh molecular weight epoxy resins as a modifier in adhesives and electrical laminates to impart flexibility and to modify the flow properties therein. The phenoxy resin provides flow control for the composition during the laminating stage which involves pressure molding of layers of substrates impregnated with the laminating varnish. This prevents the resin from flowing out of the press or mold which prevents resin poor areas in the resultant laminate. While the phenoxy resins employed provide for good flow control during molding or pressing of the impregnated substrates, the resultant laminates exhibit a decrease in one or more of their mechanical properties such as, for example, glass transition temperature, moisture and blister resistance and flame retardant properties.
The present invention provides a method for eliminating or decreasing the loss in one or more of the physical properties such as, for example, glass transition temperature, moisture and blister resistance and flame retardant properties by employing as the phenoxy resin a halogenated phenoxy resin.